feat(media): implement integrated media manager with sidebar and picker

- Implement DriveService and ShopifyMediaService for backend operations
- Create MediaSidebar.html with premium UI and auto-polling
- Integrate Google Picker API for robust file selection
- Orchestrate sync logic via MediaService (Drive -> Staged Upload -> Shopify)
- Add secure config handling for API keys and tokens
- Update ppsscript.json with required OAuth scopes
- Update MEMORY.md and README.md with architecture details

src/services/MediaService.test.ts

@@ -0,0 +1,55 @@
+import { MediaService } from "./MediaService"
+import { MockDriveService } from "./MockDriveService"
+import { MockShopifyMediaService } from "./MockShopifyMediaService"
+import { INetworkService } from "../interfaces/INetworkService"
+import { Config } from "../config"
+
+class MockNetworkService implements INetworkService {
+  lastUrl: string = ""
+  lastPayload: any = {}
+
+  fetch(url: string, params: GoogleAppsScript.URL_Fetch.URLFetchRequestOptions): GoogleAppsScript.URL_Fetch.HTTPResponse {
+     this.lastUrl = url
+     this.lastPayload = params.payload
+     return {
+         getResponseCode: () => 200
+     } as GoogleAppsScript.URL_Fetch.HTTPResponse
+  }
+}
+
+describe("MediaService", () => {
+  let mediaService: MediaService
+  let driveService: MockDriveService
+  let shopifyService: MockShopifyMediaService
+  let networkService: MockNetworkService
+  let config: Config
+
+  beforeEach(() => {
+    driveService = new MockDriveService()
+    shopifyService = new MockShopifyMediaService()
+    networkService = new MockNetworkService()
+    config = { productPhotosFolderId: "root" } as Config // Mock config
+
+    mediaService = new MediaService(driveService, shopifyService, networkService, config)
+  })
+
+  test("syncMediaForSku uploads files from Drive to Shopify", () => {
+    // Setup Drive State
+    const folder = driveService.getOrCreateFolder("SKU123", "root")
+    const blob1 = { getName: () => "01.jpg", getMimeType: () => "image/jpeg", getBytes: () => [] } as unknown as GoogleAppsScript.Base.Blob
+    driveService.saveFile(blob1, folder.getId())
+
+    // Run Sync
+    mediaService.syncMediaForSku("SKU123", "shopify_prod_id")
+
+    // Verify Network Call (Upload)
+    expect(networkService.lastUrl).toBe("https://mock-upload.shopify.com")
+    // Verify payload contained file
+    expect(networkService.lastPayload).toHaveProperty("file")
+  })
+
+  test("syncMediaForSku does nothing if no files", () => {
+      mediaService.syncMediaForSku("SKU_EMPTY", "pid")
+      expect(networkService.lastUrl).toBe("")
+  })
+})